1. Field of the Invention
The present invention relates to a 4-state bar code printing and reading system for use in physical distribution-related services such as mail pieces, receptacles, reception and management forms or the like, and a method for controlling the system.
2. Background of the Related Art
Up to now, a bar code has generally been used to facilitate automation in sorting small and large commercial mail pieces, the bar code including useful information which is associated with different patterns of varying stripes with decimal digit or decimal digits and alphabetic characters. In particular, since the bar code used in the automatic mail pieces sorting process has to be constructed to satisfy a requirement such as a size of the mail piece, a printed location of the bar code, and the like, it cannot contain a lot of information. In case of U.S. Postal Service (USPS), a bar code of Postal Numeric Encoding Technique (POSTNET) is printed on a right lower corner for automatically sorting the mail pieces, while a PLANET bar code which the POSTNET bar code is inversely converted on a right upper corner of a zip code region to provide an additional service.
With the above system, there is a problem of increasing the cost for printing and reading the bar code as much as twice. In addition, in order to provide another service, another bar code will additionally be printed on the mail piece. Further, there is another method that the customer prints a two-dimensional bar code on the mail piece for freepost or metered mail.
In the above case, since at least two bar codes must to be read, it increases the time required to read the bar code, thereby decreasing the amount of mail pieces to be processed. In addition, since a separate reader for each bar code has to be used, there is another drawback that the expenses for processing the mail pieces are increased. Further, in case that a bar code label is printed and adhered by customers (mailers) to encode sorting information, if the label is out of the straight or is disordered, there is another problem large volumes of mail pieces which are to be manually verified are provided.
Among conventional methods for reading a bar code, in case that the bar code is sloped, two methods have been proposed as follows: a slope value of the bar code is evaluated, and then the bar code is read by inversely rotating the image by the slope angle; and the bar code is read by evaluating a center axis value of one bar code. According to the above reading methods, because all of the information within the range which is divided into areas based on the center axis has to be searched, too much time is required to acquire the information for reading the bar code.
In addition, according to one prior method for tracking the slope value, if a diverse image is provided between the bars, it is impossible to read the bar code due to the variation of the thickness of the bar and the space value, or since many reference data are provided for correcting the error, an error correcting level has to be set to a high point. Therefore, in order to record much information using the bar code, a surface area to be printed is expanded. And also, in order to improve a reading efficiency, the number of codewords for correcting an error is increased. Specifically, the diverse image produced due to the bad print of the bar code causes the reading efficiency to be decreased. Furthermore, there is no a method for restoring an erased region. The mail pieces which are not automatically sorted are increased, thereby requiring the manual verification process.
Meanwhile, a Reed-Solomon which is proposed by Reed and Solomon is an RS code which is a kind of BCH (Bose-Chaudhuri-Hochquenghem) code capable of correcting an error of a concatenated pattern. The RS code can correct an error of sporadic pattern (substitution error) and an error of concatenated pattern (erasure error), and is very important code used widely. Therefore, the RS code has been studied by many coding theorists.
If the Reed-Solomon algorism is employed to correct the error, although there is no an error, a function of the error correction is called and performed. The location of the error is deviated from a range of an error correction depending upon the start position of erased bar or a unit of bar. Therefore, since the error is not corrected, manual verification process is required.